Laca has survived because everyone from Wenger, Emery to Arteta wanted someone to hold up play. The funny thing is that wasn’t even a strength of Laca when he arrived, it’s something he had to develop.
I have to say I think the mistake was absolutely signing Laca rather than not getting rid sooner. You can’t keep signing players and then getting rid. Bear in mind even good signings can take at least a couple of years to work out. That’s an enormous waste of time.
If you want to be successful you need to have a really high success rate with your signings, I don’t think the idea that you just get rid of signings who don’t work out is one grounded in reality.